There are known in the prior art various instruments for affording a measure of the smoothness of a moving web such, for example, as a web of paper or the like. Some of these instruments are laboratory or offline instruments which afford a relatively accurate indication of the smoothness of the web. Such instruments are not especially useful for providing a continuous indication of smoothness of a moving web in a production process.
Also known in the prior art are online instruments for affording a continuous measure of the smoothness of a web in a production process. While such instruments are generally satisfactory, they are not as sensitive as is desirable. More particularly, they are relatively insensitive to variations in smooth grades of paper.